Zhanghe River, located in Zhangxi 'an County, Gansu Province, is a tributary of Bangsha River, a tributary of Weihe River, a tributary of the Yellow River. It originated from Muzhailing and was handed over from Zhangxi 'an County and Minxian County. From southwest to east, it flows through the five towns of Dacaotan, Wuhu Bridge, Sancha, Yanjing and Wuyang in Zhang Xi 'an County, and flows into Bangsha River in Dingjiamen, Gaolou Township, Wushan County, which is a secondary tributary of Weihe River. Watershed area 1270.05 km2. The total length of the river is 83.7 kilometers, the riverbed gradient is 1% ~ 5%, and the drainage area is 1270.05 square kilometers.
Zhanghe River is the "mother river" of Zhangxi 'an County, and there are many irrigation canals in the basin, which is an important water source for industrial and agricultural production in this county. From the Ming Dynasty to the Qing Dynasty and the Republic of China, the timber produced in Zhangxi 'an County followed the Zhanghe River, Longchuan River and Bangsha River, entered the Weihe River in yuanyang town, Wushan County, and reached Wushan, Gangu, Tianshui, Baoji and Xianyang.
Located in the north of China, the Yellow River is one of the longest rivers in the world and the second longest river in China. The "yellow" of the Yellow River is actually sediment. The ancient book says: "The Yellow River fights water, and mud ranks seventh." 90% of the sediment of the Yellow River comes from the Loess Plateau, where the soil is loose and easy to erode and disperse. Whenever it is washed by heavy rain, it will lose a lot of soil and water and flow into the Yellow River. The river basin is long in winter and short in summer, with large temperature difference between winter and summer and obvious seasonal temperature change.
The Yellow River originates from the Yogu Zonglie Basin at the northern foot of Bayan Kara on the Qinghai-Tibet Plateau, flows through nine provinces (autonomous regions) of Qinghai, Sichuan, Gansu, Ningxia, Inner Mongolia, Shanxi, Shaanxi, Henan and Shandong from west to east, and finally flows into the Bohai Sea. The total length of the Yellow River is about 5,464 kilometers, and the basin area in People's Daily is about 752,443 square kilometers, while the total basin area recorded on the website of the Ministry of Water Resources is 795,000 square kilometers (including 42,000 square kilometers of internal flow area).
Hydrological characteristics of Zhanghe River;
According to Zhangxi 'an County Records, the average annual flow of Zhanghe River is 7.362 cubic meters, the low water flow is 0.29 cubic meters, the average annual runoff is 240.8 million cubic meters, the hydropower reserve is 42,857 kilowatts, the annual sediment discharge is 1.0 1.2 million tons, and the average annual sediment concentration is 4.98 kg/cubic meter.
Zhanghe River is prone to floods. Floods occur in spring, because ice and snow melt, and in summer and autumn, because of heavy rain. From the time point of view, it is mostly in June, July, August and September, which has the characteristics of long duration, great interannual change and high river sediment concentration. In addition, in the lower reaches of the Zhanghe River, due to the sudden change of riverbed gradient, the difference between the river elevation and the elevation of both banks is small, and whenever there is a flood, the harm of diversion and flood often occurs. The maximum flood peak appeared on August 26th, 1973. After calculation, the flow of Zhanghe River is 575 cubic meters per second.